Adjusting a Cooling Device and a Server in Response to a Thermal Event

ABSTRACT

In an electronic device enclosure, in response to a thermal event or a power event, an output of a cooling device and an operation of at least one of a plurality of electronic devices are adjusted. The adjustment of the output of the cooling device and operation of the at least one of the electronic devices is according to a policy that considers power consumption of the cooling device and the electronic devices.

CROSS-REFERENCE TO RELATED APPLICATION

This claims the benefit under 35 U.S.C. §119(e) of U.S. ProvisionalApplication Ser. No. 60/943,401, entitled “Moderating Aggregate ServerSpeed in a Bladed Environment as a Thermal Response,” filed Jun. 12,2007, which is hereby incorporated by reference.

BACKGROUND

For enhanced space efficiency while achieving increased processingpower, server enclosures (e.g., cabinets, racks, etc.) capable ofreceiving multiple servers (e.g., such as in the form of server blades)are used. A server enclosure can have multiple slots or other mountingmechanisms to receive corresponding servers.

Concerns associated with a server enclosure that has a relatively largenumber of servers include power consumption and elevated temperature.Controllers in some conventional server enclosures simply react to hightemperature levels within the server enclosures by increasing speeds offans used to cool the server enclosures until temperature levels arelowered to below target levels. If higher fan speeds cannot adequatelylower temperature levels, then the servers in the server enclosure willsimply overheat and shut down, which is a condition that is undesirablesince the servers that have shut down will become unavailable andtherefore will interfere with enterprise operations.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are described, by way of example, withrespect to the following figures:

FIG. 1 is a block diagram of an example arrangement of server enclosure,where at least one of the server enclosures incorporates componentsaccording to an embodiment; and

FIG. 2 is a flow diagram of a process of handling a thermal event,according to an embodiment.

DETAILED DESCRIPTION

In accordance with some embodiments, a technique or mechanism ofhandling a thermal (or power) event in an electronic device enclosure isprovided. An “electronic device enclosure” refers to any structure, suchas a cabinet, rack, and so forth, that defines a space to receivemultiple electronic devices. Examples of electronic devices includeserver computers (or simply servers), switch modules, communicationsmodules, storage devices, and so forth.

A “thermal event” refers to the occurrence of a condition in which atemperature level of at least some part of the electronic deviceenclosure is (or will be) at a level that exceeds a threshold. Exceedinga threshold means that the level is either greater than or less thansome predefined amount. For example, some part of the electronic deviceenclosure may overheat and cause a temperature level to be greater thansome temperature threshold (in which case actions would have to taken toallow the temperature level of the corresponding part of the electronicdevice to fall to a level below the temperature threshold). As anotherexample, a temperature level in a part of the electronic deviceenclosure may fall below some low temperature threshold, in which casean action can be taken to reduce cooling device output to reduce powerconsumption.

A “power event” refers to an event in which power consumption hasexceeded a power threshold (e.g., greater than or less than the powerthreshold).

In the ensuing discussion, reference is made to a “server enclosure,”which is an enclosure to receive multiple servers. However, note thatthe same techniques or similar techniques can be applied to enclosuresfor other types of electronic devices.

In response to detecting a thermal (or power) event in the serverenclosure, an output of a cooling device and an operation of at leastone of the servers can be adjusted, such as by a controller within theserver enclosure. The adjusting of the output of the cooling device andoperation of the at least one of the servers is according to a policythat considers power consumption of the cooling device and the servers.One example of a cooling device is a fan for generating air flow withinat least a part of the server enclosure to cool that part of the serverenclosure. Another example of a cooling device is a device that cangenerate a flow of refrigerant through refrigerant conduits to parts ofthe server enclosure. Yet another example of a cooling device is an airconditioning device that is able to generate cooled air (havingtemperature less than ambient air) and that includes some type of airblower to create a flow of the cooled air to a part of the serverenclosure.

An issue associated with a server enclosure is that the power supply (orpower supplies) within the server enclosure is (are) able to produce upto some maximum amount of power. Therefore, processing of thermal orpower events should consider such maximum power output of powersupply(ies). For example, a policy to be considered by a controller forprocessing a thermal or power event can attempt to budget more power forservers in the server enclosure while budgeting less for cooling devicepower. In other words, the policy may attempt to keep the coolingdevices operating at less than their respective maximum levels toachieve power savings, where the saved power can be re-deployed to othercomponents of the server enclosure, including the servers.

Moreover, by keeping the cooling devices in the server enclosure at lessthan their respective maximum levels, some headroom exists to allowoutputs of the cooling devices to be increased (e.g., the RPM orrevolutions per minute output of fans can be increased) to providefurther cooling capability in different parts of the server enclosure,should temperature levels rise in such parts of the server enclosure.

In addition, the policy that governs the controller in responding to athermal or power event can also specify that the thermal or power eventis to be processed by reducing operation of at least one of the servers,where reducing the operation can include any one or more of thefollowing: (1) reducing clock speed of the server; (2) reducing the dutycycle of the server; (2) reducing the number of tasks executed by theserver; or (3) otherwise modifying operation of the server such thatheat generation of the server is reduced.

The policy can also specify that the thermal or power event is to beprocessed by increasing the output of cooling devices. The policyconsiders power consumption of the servers and cooling devices indetermining the optimal balance between reducing server operations andcooling device outputs in responding to a thermal or power event.

FIG. 1 illustrates example components of a server enclosure 100. Notethat the server enclosure 100 can be connected to a data network 102,which is further connected to other server enclosures 104 and 106. Theserver enclosures 104 and 106 can have similar components as the serverenclosure 100, or alternatively, the server enclosures 104 and 106 canhave different components.

The server enclosure 100 includes a number of servers 108, which can bein the form of server blades. A server blade includes a thin, modularchassis housing that contains components such as processors, memory,network controllers, and input/output (I/O) components. The server bladeprovides processing power in a smaller amount of space. The serverblades can be mounted in corresponding slots or other mountingmechanisms in the server enclosure 100.

The server enclosure 100 also includes a cooling subsystem 110, whichincludes a number of fans 112 or other types of cooling devices. Theoutputs of the fans 112 can be adjusted to provide different levels ofcooling. For example, the revolutions per minute (RPMs) of fans can beadjusted to provide different air flow rates to achieve differentcooling targets. The server enclosure 100 also includes a powersubsystem 114, which can contain one or more power supplies 116A, 116B.In one implementation, the power supplies 116A, 116B are redundant powersupplies, where one power supply can take over for the other powersupply in case of failure of the other power supply.

Generally, within the server enclosure 100, the server blades 108 sharea common cooling subsystem (110) and a common power subsystem (114).

The server blades 108 also include respective temperature sensors 118for detecting temperatures in the server blades 108. Each sever blade108 can have one or multiple temperature sensors. Although not depicted,there may also be temperature sensors outside the server blades.Moreover, the server enclosure 100 can also include power sensors 119 todetect power consumption by different parts of the server enclosure 100.The power sensor 119 can be, for example, a current sensor.

The server enclosure 100 further includes a controller 118 that performsmanagement tasks with respect to the components of the server enclosure100. The controller 118 is able to communicate with the server blades108, cooling subsystem 110, power subsystem 114, temperature sensors118, and power servers 119 over one or more internal buses of the serverenclosure 100.

The controller 118 includes an administrator 120, which can be asoftware module (or collection of software modules) executable on one ormore central processing units (CPUs) 122 that is (are) connected tomemory 124. The administrator 120 can handle thermal or power eventswithin the server enclosure 100, in accordance with some embodiments.

The controller 118 (and more specifically the administrator 120) is ableto monitor power consumption by the server blades 108 (using the powersensors 119, for example), monitor fan speeds, detect for failure ofcomponents within the power subsystem 114, and monitor temperaturemeasurements taken by the temperature sensors 118 provided at variouslocations of the server enclosure 100. In response to a thermal or powerevent detected by the administrator 120, the administrator 120 accessesa policy (or policies) 125 maintained in the memory 124 to performresponsive actions.

The policy 125 maintained by the administrator 120 factors in powerconsumptions of the server blades 108 and fans 112 in making adjustmentsof operation of one or more of the server blades 108 and speeds of oneor more of the fans 112. According to the policy 125, the administrator120 can initially set the fans to provide reduced outputs (less thanmaximum outputs) to provide headroom to allow for the fans outputs to beincreased. Moreover, by keeping the initial speeds of the fans at alower level, more power of the power subsystem 114 can be made availablefor operation of the server blades 108, since the power subsystem 114has a finite amount of power that has to be shared by the server blades108 and the fans 112 (along with other components of the serverenclosure 100).

Note that the finite amount of power of the power subsystem can be themaximum amount of power that can be produced by one of plural redundantpower supplies (e.g., power supplies 116A, 116B).

The administrator 120 is also able to monitor advertisements of theserver blades 108 regarding how much power is needed by the serverblades 108. Therefore, before the administrator 120 allows a serverblade 108 to turn on, the administrator 120 can determine whethersufficient power exists to satisfy what the server blade has advertised.If insufficient power is present, then the administrator 120 can preventthe server blade 108 from turning on, or alternatively, theadministrator 120 can reduce power consumption elsewhere in the serverenclosure 100 to provide additional power to allow the server blade 108to turn on.

The administrator 120 can also monitor the percentage of the fan speedthat has been used. This allows the administrator 120 to determine atany given time how much additional available cooling capacity exists fordifferent parts of the server enclosure 100.

The policy 125 can also specify that the total power consumed by theserver blades 108, fans 112, and other components of the serverenclosure 100 should not exceed the maximum capacity of one of the powersupplies 11 6A and 11 6B (assuming that the power subsystem 114 includesjust two power supplies). This is to ensure that if one of the powersupplies 116A and 116B should fail, the other power supply can takeover, and the server enclosure 100 can continue to operate. A similarpolicy can be provided in a power subsystem that has more than two powersupplies, with one of such power supplies designated as the failoverpower supply.

In accordance with some embodiments, at least some of the server blades108 are capable of supporting capping. Capping refers to specifying someupper power level above which the server blade 108 will not cross. Insome implementations, there are two types of capping: (1) thermalcapping and (2) electrical capping. Electrical capping specifies a powercap (e.g. in terms of watts or amperage) that the server blade will notexceed. Thermal capping refers to an aggregate power value averaged oversome time duration that is useful for thermal planning. Thus, over agiven time duration, the server blade that is subject to thermal cappingwill not have an aggregate power value that exceeds some predefinedthreshold. The cap is indicated by a cap setting, which can be stored asa value in a storage element (e.g., register, buffer, etc.) of a serverblade.

Some of the server blades 108 may not have capping capabilities. Theadministrator 120 is able to determine which of the server blades hascapping capabilities, and which of the server blades do not. Theadministrator 120 can make this determination by submitting a requestfor the capping capability of each server blade 108. The administrator120 can also request the capping mode (thermal capping mode orelectrical capping mode) of the server blade. Moreover, theadministrator 120 can request the current cap setting (e.g., powerconsumption cap).

One technique that can be used by the administrator 120 to reduce powerconsumption by a server blade in response to a power event or a thermalevent is to reduce the current cap setting of one or more server blades.In response to a reduced cap setting, a server blade will automaticallyreduce power consumption, such as by performing clock throttling at theserver, or scheduling less tasks to be performed by the server blade.Clock throttling refers either to reducing the frequency of a clock thatis provided to components of the server blade, or reducing the dutycycle of the clock provided to such components. Reducing the duty cycleof a clock means that the ratio of the active period of the clock to theinactive period of the clock is reduced.

Alternatively, instead of adjusting the cap setting of a server blade,the administrator 120, through the controller 118, can adjust the valueof one or more input pins of processors on the server blades 108. Forexample, one such input pin can be an input pin that can indicate thatthe processor is to be in an active state or a low power state. A lowerpower state refers to a reduced activity state (or off state) in whichpower consumption of the processor is reduced. An active state refers toa state in which the processor is allowed to operate at full capacity ifdesired.

Other techniques of reducing or increasing power consumption of a serverblade can be performed in other implementations. Power consumption of aserver blade is reduced by setting a lower cap setting, or setting theinput pin(s) of processor(s) on the server blade to cause theprocessor(s) to enter a low power state. Increasing power consumption ofa server blade refers to increasing the cap setting, or setting anotherstate of the input pin(s) of the processor(s) on the server blade tocause the processor(s) to enter an active state.

FIG. 2 shows a flow diagram of a general process according to anembodiment. Initially, the administrator 120 retrieves (at 202)information regarding the server blades and fans. In someimplementations, the retrieval of information regarding the serverblades can include retrieving capping capabilities, capping mode, andcurrent cap settings of the server blades. The information retrieved forthe fans includes the percentage of fan speed that is being used by eachof the fans.

Next, according to the policy (e.g., policy 125 in FIG. 1), theadministrator 120 sets (at 204) fan speeds and server blade settings.Initially, the fan speeds of the fans of the cooling subsystem 110(FIG. 1) can be set at less than maximum speeds of the fans, to provideadditional headroom in case additional cooling is desirable. Also, theadministrator 120 can specify different cap settings for the serverblades depending on one or more various factors, such as workloads ofthe server blades.

Next, the administrator 120 monitors (at 206) for an event, which can beeither a thermal event or a power event. A thermal event may be atemperature measured by a temperature sensor exceeding some threshold.The power event may be a power consumption of a component (e.g., serverblade) exceeding some threshold.

In response to the thermal or power event, the administrator 120 adjuststhe server blade(s) and/or fan(s) according to the policy 125. Thepolicy 125 may specify that fans are to be maintained at low speeds, andthat server blades are to be throttled in the event of the thermal orpower event. Alternatively, the policy 125 can specify that the serverblades are to be throttled only after the highest fan speeds are unableto reduce temperature levels adequately in the server enclosure 100.

In one specific example, a thermal event may be indicated by excessivetemperature within a particular server blade (as detected by thetemperature sensor 118 within the server blade). In this example, theadministrator 120 can increase the speed of the fan that has beenpreviously determined to directly affect the thermal characteristics ofthe server blade that has signaled the thermal event. A fan isconsidered to directly affect the thermal characteristics of the serverblade if an increase in the fan speed results in a decrease intemperature of the server blade.

Alternatively, or additionally, in response to the thermal event fromthe particular sever blade, the administrator 120 can also increase thespeed of fans previously determined to directly affect the thermalcharacteristics of server blades adjacent the particular server bladethat signaled the thermal event.

Moreover, the administrator 120 can also signal throttling of theparticular server blade and/or its neighbors to reduce temperature.

The policy 125 specifies that some maximum power consumption levelshould not be exceeded according to the adjustments of cooling deviceoutputs and server blade operations. As noted above, the power subsystem114 can be able to specify some maximum power output, such that theaggregate of power consumption by the cooling devices, server blades,and other components of the server enclosure 100 should not exceed thismaximum power level. Note that the maximum power level can be themaximum power level of one of multiple redundant power supplies.Maintaining the aggregate power consumption within the server enclosure100 to be less than this maximum power level of one of multipleredundant power supplies allows for a different power supply to takeover provision of power in the server enclosure 100 in case anotherpower supply fails.

Note that the policy 125 can be updated based on actual operation of thecomponents of the server enclosure 100. Updating such policy 125 refersto training the policy 125 (or more specifically, the algorithmspecified by the policy 125) to enhance efficiencies and operations ofthe server enclosure 100. For example, based on actual operations of theserver enclosure 100, the administrator 128 may detect optimal balancesof cooling device outputs and server blade operations under differentconditions. The policy 125 can then be updated to reflect the possibledifferent scenarios that can be faced by the server enclosure 100. Whenthe administrator 120 subsequently detects one of such scenarios ispresent, the administrator 120 can then make adjustments of coolingdevice outputs and server blade operations accordingly.

Instructions of software described above (including administrator 120 ofFIG. 1) are loaded for execution on a processor (such as one or moreCPUs 122 in FIG. 1). The processor includes microprocessors,microcontrollers, processor modules or subsystems (including one or moremicroprocessors or microcontrollers), or other control or computingdevices. A “processor” can refer to a single component or to pluralcomponents.

Data and instructions (of the software) are stored in respective storagedevices, which are implemented as one or more computer-readable orcomputer-usable storage media. The storage media include different formsof memory including semiconductor memory devices such as dynamic orstatic random access memories (DRAMs or SRAMs), erasable andprogrammable read-only memories (EPROMs), electrically erasable andprogrammable read-only memories (EEPROMs) and flash memories; magneticdisks such as fixed, floppy and removable disks; other magnetic mediaincluding tape; and optical media such as compact disks (CDs) or digitalvideo disks (DVDs). Note that the instructions of the software discussedabove can be provided on one computer-readable or computer-usablestorage medium, or alternatively, can be provided on multiplecomputer-readable or computer-usable storage media distributed in alarge system having possibly plural nodes. Such computer-readable orcomputer-usable storage medium or media is (are) considered to be partof an article (or article of manufacture). An article or article ofmanufacture can refer to any manufactured single component or multiplecomponents.

In the foregoing description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those skilled in the art that the present invention may bepracticed without these details. While the invention has been disclosedwith respect to a limited number of embodiments, those skilled in theart will appreciate numerous modifications and variations therefrom. Itis intended that the appended claims cover such modifications andvariations as fall within the true spirit and scope of the invention.

1. A method for use in an electronic device enclosure, comprising: monitoring for an event in the electronic device enclosure that includes a plurality of electronic devices, wherein the event includes one of a thermal event and a power event; and in response to the event, adjust an output of a cooling device in the electronic device enclosure, and adjust an operation of at least one of the electronic devices, wherein adjusting the output of the cooling device and operation of the at least one of the electronic devices is according to a policy that considers power consumption of the cooling device and the electronic devices.
 2. The method of claim 1, further comprising providing a cooling subsystem including a plurality of cooling devices that are shared by the plurality of electronic devices.
 3. The method of claim 1, further comprising monitoring an output level of the cooling device, wherein adjusting the output of the cooling device and operation of at least one of the electronic devices is based further on the monitored output level of the cooling device.
 4. The method of claim 1, further comprising: determining power consumption of the cooling device and of the electronic devices, wherein adjusting the output of the cooling device and operation of at least one of the electronic devices is further based on the determined power consumption.
 5. The method of claim 4, further comprising: determining a maximum power output of a power supply subsystem, wherein adjusting the output of the cooling device and the operation of the at least one of the electronic devices is further according to the determined maximum power output of the power subsystem.
 6. The method of claim 5, wherein the maximum power output of the power subsystem is the maximum power output of one of plural redundant power supplies in the power subsystem, wherein adjusting the output of the cooling device and the operation of the at least one of the electronic devices is further based on ensuring that one of the plural redundant power supplies can continue to provide power to the electronic device enclosure in case of failure of at least one other of the power supplies in the power subsystem.
 7. The method of claim 1, further comprising: initially setting the cooling device to provide an output at less than a maximum output of the cooling device to reduce power consumption and to allow for additional power availability to the electronic devices.
 8. The method of claim 1, wherein adjusting the operation of the at least one of the electronic devices comprises adjusting a cap setting of the at least one of the electronic devices.
 9. The method of claim 8, wherein adjusting the cap setting comprises adjusting an electrical cap setting.
 10. The method of claim 8, wherein adjusting the cap setting comprises adjusting a thermal cap setting.
 11. The method of claim 8, further comprising sending a request to the electronic devices to determine respective cap settings of the electronic devices.
 12. The method of claim 1, wherein adjusting the operation of the at least one of the electronic devices comprises adjusting a state of an input to the at least one of the electronic devices to cause the at least one of the electronic devices to transition between an active state and a low power state.
 13. The method of claim 1, further comprising updating the policy according to monitored operations of components in the electronic device enclosure.
 14. The method of claim 1, wherein the electronic device enclosure includes multiple cooling devices, the method further comprising: detecting failure of one of the cooling devices, wherein adjusting the output of the cooling device and operation of the at least one of the electronic devices is further based on detection of the fan failure.
 15. The method of claim 1, wherein the electronic device enclosure comprises plural cooling devices corresponding to respective electronic devices, wherein the event includes a thermal event signaled by a temperature sensor in a particular one of the electronic devices, wherein adjusting the output of the cooling device comprises adjusting the output of at least one of the cooling devices corresponding to the particular electronic device and an electronic device adjacent the particular electronic device, and wherein adjusting the operation of the at least one of the electronic devices comprises adjusting the operation of at least one of the particular electronic device and an electronic device adjacent the particular electronic device.
 16. An electronic device enclosure comprising: a cooling device; a plurality of electronic devices; and a controller to: monitor for an event in the electronic device enclosure, wherein the event includes one of a thermal event and a power event, in response to the event, adjust an output of the cooling device, adjust an operation of at least one of the electronic devices, wherein the controller adjusts the output of the cooling device and operation of the at least one of the electronic devices according to a policy that considers power consumption of the cooling device and the electronic devices.
 17. The electronic device enclosure of claim 16, wherein the operation of the at least one of the electronic devices is adjusted by performing clock throttling at the at least one of the electronic devices.
 18. An article comprising at least one computer-readable storage medium containing instructions that when executed cause a controller in an electronic device enclosure to: store a policy that specifies how cooling devices and electronic devices in the electronic device enclosure are to be adjusted in response to an event that includes one of a thermal event and a power event, wherein the policy considers power consumption of the cooling device and the electronic devices; monitor for a thermal event or power event in the electronic device enclosure; and in response to the event, adjust the cooling device and at least one of the electronic devices according to the policy.
 19. The article of claim 18, wherein the instructions when executed cause the controller to further: receive measurement information from temperature sensors and power sensors, wherein adjusting the cooling device and the at least one of the electronic devices is further based on the received measurement information.
 20. The article of claim 18, wherein adjusting the at least one electronic device comprises changing a cap setting of the at least one electronic device, the cap setting indicating a maximum power consumption of the at least one electronic device. 